A recently filed application, Ser. No. 117,174 filed Nov. 5, 1987 in the name of William Michael Glasheen entitled: "Monolithic Faraday Optical Switch" assigned to the General Electric Company, the assignee of the instant invention, describes a monolithic Faraday effect optical switch. The monolithic switch contains all of the functional elements; viz, polarizers, analyzers, Faraday rotator layers, the light reflecting surface on a single substrate.
Briefly, the monolithic Faraday effect optical switch described in the above identified application is constructed with Faraday rotating layer(s) deposited on an optically inactive substrate. A polarizer-analyzer pair is deposited in a side-by-side arrangement on one side of the substrate over a Faraday rotator layer. A non-magnetic reflecting surface is deposited on the other side of the substrate. Radiation from an input optical fiber is transmitted through the polarizer element, through the Faraday rotational layer (s) and the optically inactive substrate to the reflecting surface where it is reflected back to the analyzer element. Being a Faraday effect device The plane of polarization of the incident radiation is rotated in the Faraday layers whenever the layer is subjected to a magnetic field. The presence of the magnetic field controls passage of light through the monolithic element thus performing the optical switching function. Because all of the functional components of the optical switch are deposited on a single substrate, a very small, miniaturized Faraday optical switching element is made possible.
Flowmeters which utilize magnetic elements positioned on the turbine and/or on the swirl generating impeller elements of the flowmeter as well known. Reference is hereby made to U.S. Pat. No. 4,301,276 issued Dec. 3, 1983 for a showing of such an arrangement. In such flowmeters mass flow is measured by measuring the time differential necessary for the magnetic elements to move through the displacement angle .theta. between the turbine and impeller or swirl generating elements; which displacement angle is a function of the fluid torque exerted on the turbine element by rotational velocity or angular momentum of the liquid being measured. Hitherto, large, and bulky sensing coils mounted on the housing of the flowmeter were used to output signal whenever the magnets passed and came into flux exchange relationship with the coil. Such arrangement were, as pointed out above, bulky and costly. A need therefore exists for a small, light weight flowmeter pick-off thereby reducing the size and weight of the flowmeter. Size and weight consideration are of great importance where mass flowmeters are utilized in aircraft, for example, where weight and size are at a premium.
Applicant has found, that the size and weight of the flowmeter arrangement may be substantially reduced by providing an optical pick-off for the flowmeter which utilizes a monolithic Faraday effect magneto-optical switch.
It is therefore a principal objective of the invention to provide a flowmeter utilizing a Faraday effect optical switch pick-off.
A further objective of the invention is to provide a flowmeter utilizing a monolithic, optical switch pick-off.
Still another objective of the invention is to produce a small, light weight flowmeter utilizing a Faraday optical switch readout.
Yet another objective of the invention is to provide a flowmeter using a Faraday effect optical switch readout which all of the functional elements of the Faraday switch are mounted on a single substrate.
Other objectives and advantages of the invention will become readily apparent as the description thereof proceeds.